This invention relates generally to baling machines typically referred to as "round balers" which form cylindrical roll bales of crop material.
In a conventional type of roll baling machine such as shown in U.S. Pat. No. 3,901,007, the upper apron moves from a starting position to a final position during formation of a roll bale in an expandable bale chamber. This movement of the upper apron is controlled by a mechanism that includes a rotatable arm assembly and extension coil springs. The arm assembly helps support the upper apron and rotates from a first position to a second position to allow the movement of the upper apron from the starting position to the final position as a bale is formed. The extension coil springs urge the arm assembly toward the first position while resisting movement thereof toward the second position. This maintains tension in the upper apron.
It is desirable for the tension in the upper apron to gradually increase during the initial and final stages of the bale forming process and to remain substantially constant during the intermediate stage of the bale forming process. This effectively controls the density of a roll bale during formation. In the baling machine shown in the above-mentioned patent, such variation in the upper apron tension is achieved by employing a rather complex arrangement of cam plates, cables and pulleys in combination with the extension coil springs which exert a constant force.
It is also desirable for the tension in the upper apron to be quickly and easly released for servicing the machine. In the baling machine shown in the above-mentioned patent, it is a difficult and lengthy procedure to release the tension in the upper apron because of the arrangement of cam plates, cables and pulleys used with the extension coil springs. Furthermore, these extension coil springs are difficult to remove from the machine because they are very bulky and heavy.